In weighing sensor technology, it is frequently required to connect components of different materials to one another, where one of the components such as, for example, a load cell is sensitive to mechanical stresses. Mechanical stresses of this type may be created when the two components are connected, or may be caused by different thermal expansions after a temperature change, namely even if the two components were connected to one another in a stress-free fashion at the initial temperature.
In an electrodynamic force compensating load cell, the lever gear is frequently machined out of an aluminum block. The base plate, in contrast, frequently consists of another material such as, for example, stainless steel. However, the entire housing of the load cell may also consist of aluminum. Further, the frame to which the load cell should be connected, for example, with the aid of screws, may be made of steel. In this case, one encounters the problem that the contact surfaces deform or even shift relative to one another if temperature changes occur. Under certain circumstances, the geometry changes or the generated mechanical stresses may extend as far as the sensor that acquires the measured values and may cause measuring errors.
In order to prevent such stresses that affect the accuracy of the sensor, German Patent Reference No. DE 10 2005 033 952 B4 proposes to fix the actual weighing system on a base plate by means of holding clamps that are connected to the base plate. The weighing system can then be connected to the holding clamps in a self-supporting fashion, for example, with the aid of screws. In this way, at least distortions of the base plate are not transmitted to the weighing system. However, thermal stresses resulting from different coefficients of expansion of the materials of the weighing system and the clamps also cannot be prevented with this type of mounting.
German Patent Reference No. DE 602 06 339 T2 discloses a mounting for a base body of an electromechanical force compensating load cell, wherein the base body features lateral flange elements that protrude over the actual load-sensing system and contain bores for mounting screws. This is intended to prevent stresses caused by the assembly from being transmitted to regions of the load cell, in which stresses can affect the accuracy of the measuring result. Since the flange elements are realized integrally with the remaining base body, however, such stresses cannot be reliably prevented.
A similar approach is described in German Patent Reference No. DE 195 35 202 C1. In this case, mounting regions are isolated by means of incisions in the base body so as to prevent stresses or distortions generated in these regions from being transmitted to the actual sensor region, i.e., the region of the base body that affects the accuracy of the measurement.
However, these known options ultimately are hardly able to prevent the measuring accuracy from being affected in load sensors or load sensor regions of weighing devices that already react sensitively to slight mechanical stresses.